This invention relates to clamping workbenches such as those of the type sold under the Trade Mark WORKMATE and in particular to a secondary clamp for attachment thereto.
The xe2x80x9cWorkmatexe2x80x9d and similar portable and collapsible clamping workbenches are now well known. Briefly, they comprise two elongate jaws supported on folding legs, interconnected by threaded rods extending transversely to the longer dimension of the jaws and rotatable by handles to enable the jaws to be relatively moved, towards or away from one another. When closed, the two jaws constitute a workbench, but by opening the jaws a workpiece can be clamped therebetween, for example for sawing or planing or otherwise working on the workpiece. Where an item is too big to be clamped directly between the jaws, it is possible to accommodate the item to be worked on by inserting pegs into the jaws, and to clamp the item between the pegs. A series of apertures have therefore been provided in the two jaws to accommodate pegs at differing distances from the inboard edges of the two jaws.
However, even if the outermost apertures in the boards are used to receive the pegs, the jaws cannot be moved apart sufficiently to enable wide sheet material to be gripped between the pegs. Typically, standard 48xe2x80x3 wide sheets of timber or laminate exceed the workpiece width which is capable of being worked upon by laying it across the workbench between pegs.
It is an object of the present invention to allow a clamping workbench to clamp an item whose width is too great to be clamped in the conventional manner by the jaws, even when fitted with the pegs.
According to a first aspect of the invention, in or for a clamping workbench comprising a main pair of jaws carried by a support, and workbench drive means for moving the main jaws towards or away from one another, a supplementary clamping jaw means is provided, adapted to be operatively joined to the main pair of jaws so as to be movable in a direction transverse to the direction of relative movement of the main jaws when the latter are relatively moved by the workbench drive means.
Typically the supplementary jaw is adapted to extend across at least in part both of the two main jaws.
It may extend perpendicularly to the main jaws or at an acute angle thereto.
In one arrangement the supplementary jaw is securable to the main jaws through a linkage which transmits the motion of the main jaws into a direction perpendicular to that motion, to produce the desired movement of the said supplementary jaw.
A second supplementary jaw may be provided, adapted to be fitted to the workbench so as similarly to extend transversely of the main jaws, but spaced from the first supplementary jaw, to allow a workpiece to be clamped between the two supplementary jaws in response to operation of the workbench drive means.
The second supplementary jaw may be adapted to be fixed to one of the two main jaws and be slidable relative to the other so as to permit the full relative movement of the two main jaws.
Alternatively where the workbench provides drive means at both ends of the main jaws for moving them together and apart, the second supplementary jaw may be adapted to be pivotally joined to both of the two main jaws at one end of the workbench whilst the first supplementary jaw is attached to the main jaws near the other end of the workbench, and when both supplementary jaws are so positioned, relative movement between the two supplementary jaws is achieved by operating the workbench drive means at the said other end of the workbench so as to increase or decrease the separation between the two main jaws at that said other end of the workbench only.
Each supplementary jaw may include a retaining lug for engaging the underside of a main jaw to prevent the supplementary jaw from lifting off the main jaws.
Each retaining lug may comprise an L-shaped bracket designed to accommodate the thickness of a main jaw between it and the underside of the supplementary jaw, or may comprise a member mounted at a distance below the supplementary jaw so as to extend below one or both of the main jaws.
To facilitate the fitting of a supplementary jaw when fitted with a retaining member, which is adapted to extend below both main jaws, the member may be movable relative to the underside of the supplementary jaw as by sliding or pivoting to assist in positioning the supplementary jaw or the main jaws.
Typically the supplementary jaw or jaws is/are located above the main jaws.
When fitted to a clamping workbench as aforesaid and mounted transversely to the main jaws thereof at a position spaced from stop means carried by the main jaws, operation of the workbench drive means in one sense will increase the distance between the supplementary jaw and the stop means (for example to allow a workpiece to be laid flat on the main jaws between the supplementary jaw and the stop means) and when operated in the opposite sense will decrease the distance between the supplementary jaw and the stop means to cause the workpiece to be gripped between the stop means and the supplementary jaw.
Conventionally the main jaws include openings into which pegs will fit, and the stop means may comprise one or more such pegs having enlarged heads to prevent them from passing completely through the openings, or the stop means may comprise a second supplementary jaw as aforesaid.
Conveniently the linkage members for mounting the supplementary jaw or jaws to the main jaws may include pegs adapted to be fitted into the stop peg openings in the main jaws.
Alternatively the end of each linkage members may be cut away to define an opening into which the enlarged head of a conventional peg can be received, the latter serving as an end stop for the linkage member.
One preferred arrangement comprises a supplementary jaw having an elongate slot in one longer edge thereof for receiving an end of a linkage arm which is secured therein for sliding and pivoting movement relative to the supplementary jaw, the other end of the linkage arm includes a peg adapted to be a push fit in an opening in one of the main workbench jaws, and the supplementary jaw includes a retention device in the form of an L-shaped bracket, one limb of which is spaced from its underside and defines therewith a channel which is adapted to engage the inner facing edge of the other of the main workbench jaws.
The spacing between the underside of a supplementary jaw and the retention device lug may be adjustable to accommodate different thicknesses of workbench jaw.
The invention finds application in particular to collapsible clamping workbenches sold under the Trade Mark xe2x80x9cWORKMATExe2x80x9d. Thus according to a further aspect of the invention, there is provided a secondary clamp for attachment to a collapsible clamping workbench sold under the Trade Mark WORKMATE, comprising a supplementary jaw and means for operatively connecting the supplementary jaw to the workbench jaws, whereby when an operating handle for moving one workbench jaw relative to the other is rotated, relative movement is effected between the said supplementary jaw and the main workbench jaws in a direction transverse to the direction of relative movement of the main workbench jaws, to enable a workpiece laid on the main workbench jaws between the supplementary jaw and stop means attached to one or both of the workbench jaws, to be clamped therebetween.
The stop means may comprise conventional xe2x80x9cWORKMATExe2x80x9d pegs fitted into openings in the main workbench jaws or an elongate stop means extending transversely of the two main workbench jaws remote from the placement of the supplementary jaw.
The said elongate stop member may be formed from a single elongate strut adapted to be fitted to the main workbench jaws or may include two shorter elongate struts, one attached to one workbench and the other attached to the other workbench jaw and aligned as required.
In one embodiment the linkage comprises a pair of levers, one for attachment to each of the workbench jaws, each lever having at one end a cylindrical peg for pivotally fitting it into a circular peg stop receiving opening in one of the workbench jaws, and remote therefrom means for effecting a pivoting and sliding connection with the transverse supplementary jaw.
As the two workbench jaws are moved apart or together, the axis of rotation of the two levers are similarly moved apart or together, the levers rotate relative to the workbench jaws about their respective peg axes, and this causes the transversely extending secondary jaw member to move in a direction at right angles to the length direction of the workbench jaws since the remote ends of the levers are held captive therein.
By providing an elongate slot for the remote end of each of the levers, these can either diverge or converge between the supplementary jaw and the workbench jaws, thereby acting in either an outward or an inward sense, so altering the direction of movement of the supplementary jaw in response to the opening and closing of the workbench jaws.
In the simplest embodiment, one supplementary jaw member is fitted to the workbench jaws at one end thereof and conventional peg stops are inserted into holes in the workbench jaws at or near the other end thereof and, as there normally exist a series of holes for peg stops in each workbench jaw, different positions are possible for both the fixed stops and the movable supplementary jaw, by utilising different pairs of the holes in the workbench jaws for the peg stops and pivot pegs of the levers.
In a preferred embodiment, an elongate stop member is provided, adapted to abut the peg stops and extend across the gap between the workbench jaws, to provide better support for the edge of a workpiece.
In a further embodiment, the elongate stop member may include a bracket to engage the inner edge of one of the workbench jaws or an elongate retaining member spaced therefrom to protrude below one or both of the main jaws, to prevent the member from lifting when under pressure.
In a further embodiment, the elongate stop member may include a peg for fitting into an opening in one of the workbench jaws. Where it is desirable not to restrict the relative movement Of the latter, and it is also desirable to provide peg engagement between the elongate stop member and both workbench jaws, a second peg is provided which is slidable relative to the elongate stop member to accommodate relative movement of the workbench jaws.
In a still further embodiment, two similar supplementary jaws are provided, for mounting at opposite ends of the workbench, so that when so mounted relative movement of the workbench jaws results in orthogonal movement of each of the two supplementary jaws, albeit in an opposite sense, so as to clamp or release their grip on a workpiece located therebetween.
Conventionally the length of the workbench jaws is significantly greater than the maximum distance between the outermost edges thereof when opened to their maximum extent, measured perpendicularly to their length. Accordingly when a supplementary jaw and cooperating end stop (such as a second supplementary jaw) are fitted into holes in the workbench jaws at the extreme ends of the jaws, and thereby spaced to the widest possible extent, the space available for a workpiece therebetween is substantially greater than the corresponding spacing available in the conventional transverse sense between stops inserted in the openings provided in the main workbench jaws.
Where only one transverse supplementary jaw is attached to one end of a workbench and is movable transversely thereto, a single handed clamping action is made possible for the user, which is especially advantageous for repetitive work, since it is only necessary to turn the workbench jaw drive handle at the said one end of the jaws.
On the other hand, where two supplementary jaws are provided, joined to opposite ends of a pair of workbench jaws, the relative movement between the workpiece engaging supplementary jaws for a given number of turns of the workpiece drive, is magnified by a factor of 2, although in order to obtain dual movement, both ends of the workbench jaws must be moved in a similar manner and therefore where separate drive handles are provided, both drive handles must be rotated simultaneously and to the same extent.
In a further embodiment, the two levers joining a supplementary jaw to the two workbench jaws may cross over at a point between their ends and be pivotally attached at the crossing point to form a scissors action. By adjusting the crossing point position, so a magnifying or demagnifying effect of the workbench jaw movement can be obtained.
It is an advantage of the invention that the presence of the primary workbench jaws below the supplementary jaw means that a narrow workpiece clamped by the supplementary jaw does not fall between the supplementary jaw and the opposite clamping device (either stop pegs or a second supplementary jaw) when the clamping force exerted by the supplementary jaw is removed.
The pivoting linkage between the workbench jaws and supplementary jaw may be arranged so that the supplementary jaw moves in a direction to clamp a workpiece when the workbench jaws are moved together and vice versa.
Where the supplementary jaw in any cooperating stop member includes a restraining device which is to underlie a workbench jaw to prevent it from lifting when a clamping pressure is applied, the connection between the upper member and the restraining device may extend through an opening in a workbench jaw or around the rear edge of the jaw or more preferably across the clamping face of the workbench jaw, and to this end the connection is preferably formed from a thin structural member such as a metal strip so that the workbench jaws can be almost closed if desired.
According to a second aspect of the invention, a supplementary clamping jaw for fitting above the workbench jaws of a clamping workbench includes drive means for shifting the supplementary clamping jaw at right angles to the direction of clamping movement of the workbench jaws in response to inward or outward movement thereof, wherein the supplementary clamp jaw drive is adapted to fit between the opposed clamping faces of the workbench jaws.
The supplementary clamp jaw drive may comprise lever means acted on by spring means to engage a clamping face of one of the workbench jaws.
Two such sprung lever means may be provided for engaging both opposed clamping faces of two workbench jaws to provide a symmetrical arrangement.
A retaining member may extend from below the supplementary clamping jaw to engage the underside of one of the workbench jaws.
Two such retaining members may be provided to form a symmetrical arrangement for engaging the undersides of both workbench jaws.
The retaining members may simply comprise elongate lips protruding laterally of a vertical support which latter is adapted to extend between the two clamping faces of the workbench jaws.
The vertical support is preferably a thin wood, plastics or metal member.
One of the workbench jaw clamping faces may be formed with a plurality of pockets spaced apart therealong and adapted to accept and retain an end of a supplementary jaw drive lever.
The pockets may be formed by openings or slots in the jaw surface or may be a ratchet attached to or embedded at least in part in the jaw surface, or a strip of wood or metal or plastics material having openings formed therein and fitted to the edge of the jaw, or a frame adapted to fit snugly over the whole workbench jaw may be provided, the outer surface of the edge which overlies the clamping face of the jaw having formed therein the openings or pockets as specified.
Where a frame is employed, means may be provided to clamp or otherwise secure the frame to the workbench jaw. Where two levers are employed in the drive, a similar arrangement is preferably provided for the other workbench jaw to provide pockets along both opposed clamping faces of the two jaws.
According to another aspect of the present invention in or for a clamping workbench having a pair of relatively displaceable jaws, and drive means for moving one of the jaws towards and away from the other (or for moving both jaws relative to each other), and in which the jaws have openings therein into which pegs can be pushed to provide workpiece end stops upstanding from the workbench jaws, there is provided an improved peg stop therefor, having an enlarged head, wherein the peg is mounted asymmetrically relative to the head.
By asymmetrically mounting the head relative to the peg, the latter can be rotatably located in an opening in the workbench and rotated therein to provide a variation in the offset between the peg axis and the workpiece engaging face of the head.
The peg and opening may be cylindrical to allow full rotation or may be square or triangular in cross-section allowing for a correspondingly limited number of orientations to be achieved by lifting the peg and reinserting it.
The invention also lies in a clamping workbench having relatively movable primary clamping jaws when fitted with at least one supplementary clamping jaw means as aforesaid, and at least one fixed stop for clamping a workpiece therebetween above the primary clamping jaws, the orthogonal movement between the supplementary clamp jaw and the fixed stop required to effect the said clamping of the workpiece therebetween being effected by a translation of the movement of the primary clamping jaws of the workbench.
The invention also lies in a clamping workbench having relatively movable primary clamping jaws when fitted with two supplementary clamping jaws as aforesaid, mounted so as to produce opposed motion of the supplementary clamping jaws in response to the said relative movement of the primary clamping jaws, the supplementary clamping jaws being spaced apart along the length of the primary clamping jaws to permit a workpiece to be located therebetween and clamped up by effecting the usual movement of the primary clamping jaws of the workbench.
The invention also lies in a clamping workbench having two relatively movable primary clamping jaws having openings therein to receive peg stops, when fitted with at least one offset peg stop member as aforesaid, with its peg in one of the peg receiving apertures and rotatable into at least two positions so as to provide two different spacings between a clamping face of the offset peg and at least one other peg stop or supplementary clamping jaw as aforesaid.
The invention also lies in a clamping workbench as aforesaid having two relatively movable primary clamping jaws in combination with at least one supplementary clamping jaw means as aforesaid, and at least one offset peg stop as aforesaid.
The invention also lies in a kit of parts comprising a clamping workbench having two relatively movable primary clamping jaws, at least one supplementary clamping jaw means adapted to be secured to one or both of the primary clamping jaws to translate normal relative movement therebetween into an orthogonal clamping movement, and at least one offset stop peg adapted for insertion into a peg receiving opening of the primary jaws and at least one conventional peg stop also adapted to be fitted into a peg retaining opening in the primary jaws of the workbench.